1. Field of the Invention
This invention relates generally to optical apparatus, and more particularly to optical apparatus which separate color images into component parts for input into electronic systems.
2. Description of the Prior Art
It is well known that the many colors of the visual spectrum can be represented by mixtures of other colors, uuch as red, green, and blue. This fact has been used to advantage in many fields. For example, in the video field, a color image can be produced on a video screen having a large number of red, green, and blue pixels. By controlling the intensity of the light emitted from each of the color pixels, images of virtually any color can be produced.
Video, of course, is not the only field which utilizes the principles of color mixing. For example, color photocopiers utilize the same principles to produce color images on pieces of paper. However, no matter the field, the problem remains on how to efficiently separate a color image into color components for efficient input into an electronic system.
Color separation filters are often used to separate light from a color image into its various color components. There are two major types of color separation filters, namely reflective filters and transmissive filters. Reflective filters tend to be used more frequently for color separation purposes, because they can split a light beam into two beams of different colors.
A problem with reflective filters is their inefficiency at eliminating unwanted spectral frequencies. For example, a red reflective filter may reflect 99.9% of the red light impinging upon it, but it also reflects 15% of the green and the blue light. Since this can cause distortion in the reproduced color image, expensive electronic circuits are often employed to electronically separate the unwanted light signals from the desired light signals.
Once the light has been separated into component color beams by the color separation filters, they are typically focused by a projection lens assembly on optical sensors. Since the sensors are invariably smaller than the source color image, the projection lens assembly de-magnifies the source color image for projection onto the sensors. Due to this de-magnification, the positions of the optical components in the image space (the space between the projection lens assembly and the sensors) is much more critical than the position of the optical components in the object space (the space between the source color image and the projection lens assembly).
Another source of color image distortion is stray light impinging upon the optical sensors. The prior art has addressed this problem by using low-reflective baffles to block undesirable stray light.